1. Field of the Invention
The present invention relates generally to a system and method for controlling temperature of an energy storage device in a vehicle, and in particular to a system and method for controlling a movable device to selectively draw air from a vehicle operator cabin toward the energy storage device.
2. Background Art
Governmental regulations and environmental concerns have dictated the need for automobile manufacturers to develop more fuel efficient powertrains. All-electric and hybrid electric powertrains are two examples of such powertrains currently under development. All electric vehicles are generally desirable in that such vehicles offer the potential to be simply regenerated by plugging into a power outlet and may completely eliminate fossil fuel dependence. However, even after many years of research, these vehicles are currently limited by current technology and only have a limited distance range. Hybrid electric vehicles possess increased fuel economy by combining the functionality of electric vehicles with internal combustion vehicles.
Hybrid electric vehicles (“HEVs”) combine an internal combustion engine or some other primary source such as a fuel cell system with a secondary power source such as a high powered battery and electric motor. This dual powering mechanism allows HEVs to have extended range and similar refueling to fossil fuel vehicles. Presently, batteries are only able to store enough energy for short trips. Therefore, the inclusion of an internal combustion engine in HEVs allows an onboard generator to recharge the battery and to be used as a power source to run the electric engine. This combination not only leads to increased energy savings but also a decrease in undesirable automobile emissions.
There are currently various designs for hybrid electric vehicles. However, HEVs generally include primary and secondary power sources, a mechanism to propel the vehicle, and one or more energy storage devices. Power sources include internal combustion engines, gas turbines, fuel cells, and the like. Electric motors are one type of mechanism used to propel HEVs and may be combined with a variety of transmission mechanisms, such as, planetary gear sets, CVTs, and other gearing for delivering tractive force to the vehicle's driveline. Although batteries are the most common energy storage devices, alternatives including ultracapacitors are possible.
The high powered batteries which are presently used tend to require cooling, because of the high current drawn to propel a vehicle, and purging of battery gases that build up around the battery. Conventional designs generally implement dedicated air conditioning units to cool/purge the battery. However, air conditioning units add cost, weight and complexity to the vehicle. In addition or in the alternative, conventional designs implement fans to draw cooled air from the vehicle operator cabin toward the battery. However, conventional designs generally implement on/off fan control that is dependent solely on the temperature of the battery. Accordingly, use of the fan may undesirably impact the temperature of the operator cabin by drawing cooled air away from the cabin and operator. Furthermore, it may be desirable to heat the high powered batteries since the discharge output and charge acceptance of a battery are reduced when the battery is cold. Conventional designs generally do not attempt to heat the battery.
Accordingly, there exists a need for improvements in all-electric (i.e., pure electric) and hybrid electric vehicle designs. In particular, there is a need for control strategies and systems that provide battery cooling, heating and/or purging while reducing negative impact on operator cabin comfort.